JP2017194547A - Method of manufacturing holographic optical element, and exposure optical devices - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method which allows stable and efficient manufacturing of a holographic optical element capable of sufficiently correcting the aberration caused by the difference between an exposure wavelength at hologram recording and a use wavelength at hologram reproduction and thus making efficient use of the light source light quantities, and also to provide exposure optical devices used for the manufacturing method.SOLUTION: The present invention relates to manufacturing of a holographic optical element having a peak of diffraction efficiency at wavelengths of RGB, in which a hologram photosensitive material HK is irradiated with RGB laser beams KR, KG, KB to record exposure at inference fringes. At that time, the laser beams KR, KG, KB are irradiated to a surface S1 of the photosensitive material. The laser beams KR, KG, KB transmitted through the hologram photosensitive material HK after the projection are reflected to re-enter the hologram photosensitive material HK. The incident angles of the laser beams KR, KG, KB on the surface S1 of the hologram photosensitive material HK are thus made different for each wavelength, so that the diffraction wavelength at hologram reproduction is individually adjusted for each wavelength.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for manufacturing a holographic optical element and an exposure optical apparatus, and is suitable for, for example, an observation optical system for an optical see-through display (eg, HMD (head mounted display), HUD (head-up display), etc.). The present invention also relates to a method for manufacturing a holographic optical element and an exposure optical apparatus used therefor.

  In the manufacture of a holographic optical element, two light beams (two-beam exposure) applied to record the interference state of light (for example, in the case of a direct reflection, a stripe having a quarter pitch of the exposure wavelength is recorded). Highly accurate stability is required for the phase difference. What individually acts on the light beam after being branched into two (for example, air fluctuation or vibration) affects the interference state of the light, so the longer the optical path after being branched into two, the more intervening The more members that are used, the more easily affected. Therefore, Patent Documents 1 to 4 propose a method of performing exposure (one beam exposure) on a hologram photosensitive material using only one light beam as a method for stably and efficiently manufacturing a holographic optical element. .

  Holographic optical elements have high wavelength selectivity, particularly when used in a reflective type. In a color holographic optical element having diffraction characteristics at a plurality of wavelengths, the diffraction behavior for each wavelength is independent due to high wavelength selectivity and can be individually controlled. However, it is difficult to sufficiently correct aberrations (color unevenness, etc.) due to deviation between the exposure wavelength at the time of hologram recording and the used wavelength at the time of hologram reproduction and to efficiently use the light source light amount in each band. For this reason, Patent Document 5 proposes a method of performing two-beam exposure so that the incident angles to the hologram photosensitive material are different from each other according to the amount of deviation during hologram recording.

JP-A-3-273276 Japanese Patent Laid-Open No. 7-104646 Japanese Patent Laid-Open No. 5-288989 JP 2002-258488 A JP 2008-191527 A

  In the holographic optical element obtained by the manufacturing method described in Patent Documents 1 to 4, correction of aberration caused by a deviation between the exposure wavelength at the time of hologram recording and the use wavelength at the time of hologram reproduction, and efficient use of the light source light amount Is difficult (for example, the display brightness is lowered), and it is difficult to stably and efficiently manufacture the holographic optical element with the manufacturing method described in Patent Document 5. .

  The present invention has been made in view of such a situation, and an object of the present invention is to sufficiently correct the aberration caused by the difference between the exposure wavelength at the time of hologram recording and the use wavelength at the time of hologram reproduction, and An object of the present invention is to provide a manufacturing method capable of stably and efficiently manufacturing a holographic optical element that can be efficiently used, and an exposure optical apparatus used therefor.

In order to achieve the above object, a method for manufacturing a holographic optical element according to a first aspect of the present invention provides a method for manufacturing a holographic optical element having diffraction efficiency peaks at a plurality of wavelengths. A manufacturing method for performing exposure recording of interference fringes by irradiating a laser beam,
Irradiating one surface of the hologram photosensitive material with a laser beam of the plurality of wavelengths, reflecting the laser beam transmitted through the hologram photosensitive material by the irradiation and re-entering the hologram photosensitive material;
The diffraction wavelength of hologram reproduction is individually adjusted for each wavelength by making the incident angles of the laser light beams having the plurality of wavelengths different from each other with respect to one surface of the hologram photosensitive material.

According to a second aspect of the present invention, there is provided a method of manufacturing a holographic optical element according to the first aspect, wherein exposure recording of the interference fringes is performed using an exposure optical device, and the exposure optical device is
A light source unit having a plurality of laser light sources with emission wavelengths corresponding to the plurality of wavelengths;
A first optical system for irradiating one surface of the hologram photosensitive material with the laser beams having the plurality of wavelengths emitted from the light source unit;
Irradiation to the other surface of the hologram photosensitive material by reflecting the laser light beams having the plurality of wavelengths that have been emitted from the first optical system and transmitted through the hologram photosensitive material and reflected again on the hologram photosensitive material. A second optical system,
The first optical system includes a combiner that superimposes the laser beams of the plurality of wavelengths, and an expander that expands the diameter of the laser beam superimposed by the combiner,
The second optical system has a reflecting surface for reflecting the laser beam;
The first optical system individually adjusts the diffraction wavelength of hologram reproduction for each wavelength by differentiating the incident angles of the laser beams of the plurality of wavelengths with respect to one surface of the hologram photosensitive material for each wavelength. Features.

  According to a third aspect of the present invention, there is provided a method for manufacturing a holographic optical element according to the second aspect, wherein the second optical system includes a reflective optical element including a curved reflective surface as the reflective surface.

  According to a fourth aspect of the present invention, there is provided a method for manufacturing a holographic optical element according to the second or third aspect of the invention, wherein the second optical system has a wavelength of the wavefronts of the plurality of wavelengths of laser beams that are incident again on the hologram photosensitive material. It is characterized by having a correction optical element that is different for each.

  According to a fifth aspect of the present invention, there is provided a method of manufacturing a holographic optical element according to the fourth aspect, wherein the correction optical element is disposed between the hologram photosensitive material and the curved reflecting surface, The transmission optical element is characterized in that each laser beam is transmitted so that the deflection direction of the beam is different, thereby making the wavefront different for each wavelength.

  According to a sixth aspect of the present invention, there is provided a method for manufacturing a holographic optical element according to the fourth aspect, wherein the correction optical element diffracts each laser beam such that the deflection directions of the laser beams having the plurality of wavelengths are different from each other. Therefore, the wavefront is a diffractive optical element that makes the wavefront different for each wavelength.

  According to a seventh aspect of the present invention, there is provided a method of manufacturing a holographic optical element according to the fourth aspect, wherein the correction optical element has a plurality of dichroic reflection surfaces that react to a specific wavelength as the curved reflection surface. A dichroic laminated mirror that is integrated with an optical element and reflects each laser beam so that the reflected wavefronts of the laser beams of the plurality of wavelengths are different from each other, thereby making the wavefront different for each wavelength. To do.

  According to an eighth aspect of the present invention, there is provided a method for manufacturing a holographic optical element according to the seventh aspect, wherein the reflection at the plurality of dichroic reflection surfaces is back surface reflection.

An exposure optical apparatus for manufacturing a holographic optical element according to a ninth aspect irradiates a hologram photosensitive material with a laser beam having a plurality of wavelengths in the manufacture of a holographic optical element having diffraction efficiency peaks at a plurality of wavelengths. An exposure optical apparatus for performing exposure recording of interference fringes,
A light source unit having a plurality of laser light sources with emission wavelengths corresponding to the plurality of wavelengths;
A first optical system for irradiating one surface of the hologram photosensitive material with the laser beams having the plurality of wavelengths emitted from the light source unit;
Irradiation to the other surface of the hologram photosensitive material by reflecting the laser light beams having the plurality of wavelengths that have been emitted from the first optical system and transmitted through the hologram photosensitive material and reflected again on the hologram photosensitive material. A second optical system,
The first optical system includes a combiner that superimposes the laser beams of the plurality of wavelengths, and an expander that expands the diameter of the laser beam superimposed by the combiner,
The second optical system has a reflecting surface for reflecting the laser beam;
In order that the first optical system individually adjusts the diffraction wavelength of hologram reproduction for each wavelength, the incident angles of the laser light beams of the plurality of wavelengths with respect to one surface of the hologram photosensitive material are made different for each wavelength. Features.

  According to the present invention, a holographic optical element that can sufficiently correct aberration due to a deviation between an exposure wavelength at the time of hologram recording and a use wavelength at the time of hologram reproduction, and that can efficiently use the light amount of the light source can be stably provided. It can be manufactured efficiently.

1 is a schematic cross-sectional view showing an exposure optical apparatus used in the manufacturing method of the first embodiment. FIG. 5 is a schematic cross-sectional view showing an exposure optical apparatus used in the manufacturing method according to the second embodiment. FIG. 10 is a schematic cross-sectional view showing an exposure optical apparatus used in the manufacturing method of the third embodiment. FIG. 10 is a schematic cross-sectional view showing an exposure optical apparatus used in a manufacturing method according to a fourth embodiment. Explanatory drawing which shows the relationship between the object light and reference light with respect to a hologram photosensitive material, and the illumination light and reproduction | regeneration light with respect to a holographic optical element. Explanatory drawing which shows the relationship between the object light at the time of hologram recording by the 1 light beam exposure method, reference light, and an interference fringe in the case of normal incidence, and the case of oblique incidence. Explanatory drawing which shows the incident angle adjustment at the time of hologram recording for correct | amending the aberration resulting from the shift | offset | difference of the exposure wavelength at the time of hologram recording, and the use wavelength at the time of hologram reproduction. Sectional drawing for demonstrating the relationship between the chromatic aberration which generate | occur | produces in a wedge prism, and the holographic optical element which corrects it. FIG. 10 is a schematic diagram showing an exposure optical apparatus for tiling used in the manufacturing methods of the fifth and sixth embodiments.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS A holographic optical element manufacturing method, an exposure optical apparatus for manufacturing a holographic optical element, and the like according to the present invention will be described below with reference to the drawings. In addition, the same code | symbol is mutually attached | subjected to the part which is the same in each embodiment etc., and the corresponding part, and duplication description is abbreviate | omitted suitably.

  First, the relationship between the object light and reference light during hologram recording and the illumination light and reproduction light during hologram reproduction will be described. FIG. 5A shows the optical paths of the object light R1 and the reference light R2 with respect to the hologram photosensitive material HK during hologram recording, and FIG. 5B shows the illumination light C1 and reproduction with respect to the holographic optical element HE during hologram reproduction. The optical path of the light C2 is shown.

The object light R1 and the reference light R2 shown in FIG. 5A are both parallel light for simplicity of description, and both are coherent light of wavelength λ emitted from the laser light source. When the object light R1 and the reference light R2 having the wavelength λ are incident on the hologram photosensitive material HK (n: refractive index), interference fringes FK are formed due to the interference. The interval (pitch) Λ and the inclination ψ of the interference fringes FK are expressed by the following equations (F1) and (F2).
Λ = λ / [2n · sin {(θr−θo) / 2}] (F1)
Ψ = (θr + θo) / 2 (F2)
However,
Λ: spacing of interference fringes FK,
Ψ: inclination angle of interference fringe FK,
θo: incident angle of object light R1 (in-medium angle),
θr: incidence angle of reference light R2 (in-medium angle),
n: refractive index of the medium,
It is.

  Here, two exposure states (FIGS. 6A and 6B) in hologram recording (FIG. 5A) are considered. As shown in FIGS. 6A and 6B, a plane mirror MR is disposed on the bottom side of the hologram photosensitive material HK, and a parallel light beam is incident on the hologram photosensitive material HK as object light R1 from a direction opposite to the plane mirror MR. Let The object light R1 passes through the hologram photosensitive material HK, is reflected by the plane mirror MR, and enters the hologram photosensitive material HK again as reference light R2. This one-beam exposure state corresponds to an exposure state by a contact copy method of a hologram.

  In the first exposure state shown in FIG. 6A, the object light R1 is perpendicularly incident on the hologram photosensitive material HK and the plane mirror MR (θo = 0 °). In the second exposure state shown in FIG. 6B, the object light R1 is obliquely incident on the hologram photosensitive material HK and the plane mirror MR with an inclination (θo> 0 °. For example, in the medium. Angle θo = 60 °).

  From the expression (F1) of the interval Λ of the interference fringes FK, the interval Λ of the interference fringes FK becomes the narrowest in the first exposure state where the object light R1 is incident perpendicularly (θo = 0 °), and the object light R1 is It can be seen that, in the second exposure state that is obliquely incident (θo> 0 °), the larger the incident angle θo, the wider. For example, when the incident angle θo = 60 ° in the medium, Λ = λ / [2n · sin {(120−60) / 2}] = Λ / (2n), and the incident angle θo = 0 in the medium. In the case of ° (normal incidence), Λ = λ / [2n · sin {(180-0) / 2}] = Λ / n. Therefore, in the case of θo = 60 °, the interval is larger than that in the case of normal incidence. Λ is doubled.

  From the equation (F2) of the inclination Ψ of the interference fringes FK, the case of the first exposure state in which the object light R1 is perpendicularly incident (θo = 0 °) and the case of the second exposure state in which the object light R1 is obliquely incident ( It can be seen that the inclination angle ψ of the interference fringes FK is the same. That is, in both exposure states, the interference fringes FK are parallel to the hologram photosensitive material HK and the plane mirror MR.

When reproducing the hologram, as shown in FIG. 5B, when the illumination light C1 is incident on the holographic optical element HE, the diffraction of the incident illumination light C1 is determined by the recorded hologram interference fringes FE. . Then, the intensity of the diffracted light (that is, the reproduction light C2) is maximized in the direction in which the following expressions (F3) and (F4) satisfying the Bragg condition are simultaneously satisfied.
(Sin θo−sin θr) / λr = (sin θi−sin θc) / λc (F3)
(Cos θo−cos θr) / λr = (cos θi−cos θc) / λc (F4)
However,
λr (nm): wavelength at the time of hologram recording (when producing the holographic optical element HE),
θo (°): incident angle (in-medium angle) of object light R1 at the time of hologram recording (when producing holographic optical element HE),
θr (°): incident angle (in-medium angle) of reference light R2 at the time of hologram recording (when producing holographic optical element HE),
λc (nm): wavelength at the time of hologram reproduction (when using the holographic optical element HE),
θi (°): incident angle (in-medium angle) of illumination light C1 during hologram reproduction (when holographic optical element HE is used),
θc (°): exit angle of reproduction light C2 (in-medium angle) during hologram reproduction (when holographic optical element HE is used),
It is.

  As is apparent from FIGS. 6A and 6B, the holographic optical element HE manufactured in any exposure state has the same inclination of the hologram interference fringe FE, and the plane mirror MR disposed below. As in, the incident illumination light C1 is diffracted and reflected in the regular reflection direction. However, the interval Λ of the produced hologram interference fringes FE is different. Therefore, for example, when the illumination light C1 is vertically incident on the holographic optical element HE produced in the second exposure state (FIG. 6B) where the object light R1 is obliquely incident (FIG. 6A). In the case of the same vertical incidence as the object light R1, the wavelength λc of the diffracted light is double the wavelength λr of the light used for hologram recording at the oblique incidence (FIG. 6B).

  For example, assuming a holographic optical element HE used at 45 ° incidence, if the wavelength λr used for hologram recording and the wavelength λc used for hologram reproduction are the same, the holographic at 45 ° incidence is the same as the usage state. The optical element HE may be manufactured. However, when the wavelength λc used for reproduction is different, this can be corrected using the relationship between the incident angle and the wavelength change. For example, if the incident angle θo of the object light R1 is increased toward the side of increasing the hologram recording, it can be corrected to increase the use wavelength λc, and the incident angle θo of the object light R1 is decreased to decrease the hologram recording. Then, it can correct | amend to the side which shortens use wavelength (lambda) c.

  Since the coherence is important for the light used for manufacturing the holographic optical element HE, a laser beam with high coherence is generally used. Therefore, the choice of the oscillation wavelength of the laser is limited depending on the type of crystal or gas of the oscillation medium in principle. For example, YAG (yttrium / aluminum / garnet crystal) or YVO4 (yttrium / vanadate crystal) is practical as a green laser, and both of them oscillate 1064 nm light and emit a double wave (wavelength 532 nm). Used as a light source for visible green.

  On the other hand, an LED (light emitting diode) is generally used as a reproduction light source of the holographic optical element HE. In particular, in the case of the reflection type holographic optical element HE, the wavelength characteristic of diffracting only light of a specific wavelength is particularly high in its diffraction characteristics. Therefore, an LED light source that emits light with a specific wavelength depending on the material is It is convenient in terms of light utilization efficiency. The emission wavelength of an LED is determined by the material of the LED, which is similar to a laser (but not as much as a laser), and the choice of emission wavelength is limited. For example, AlAs is one of the representative materials for visible green, and its emission wavelength peak is around 520 nm, which is different from the oscillation wavelength of a general green laser. The wavelengths of the laser and the LED rarely coincide with each other, and not only for green (G) but also for the blue (B) and red (R) regions necessary for colorization, for example. Since this is a problem caused by each material, the amount of deviation is not regular.

  When it is desired to perform diffraction at a desired angle with the holographic optical element HE, if the optimum diffraction wavelength and the light emission wavelength used are different, the light utilization efficiency is reduced (for example, the display luminance is lowered). .) For example, in the case of a color hologram that diffracts at different wavelengths, there is no regularity in the amount of deviation in each of red, green, and blue, so matching with the light source wavelength used varies, and a desired holographic optical element HE is desired. Even if diffraction efficiency is given, it leads to color unevenness and deterioration of color balance. In order to optimize the matching in each color, it is necessary to individually correct aberrations (color unevenness, etc.) caused by the deviation in each color.

  As described above (FIGS. 6A and 6B), in the one-beam exposure method, by adjusting the incident angle θo of the object light R1 at the time of hologram recording, the exposure wavelength λr at the time of hologram recording and at the time of hologram reproduction are adjusted. It is possible to correct the aberration caused by the deviation from the used wavelength λc and to efficiently use the light source light amount. In the case of a color hologram, the incident angle θo of the object light R1 at the time of recording the hologram may be individually controlled so as to achieve a desired correction at each wavelength. The one-beam exposure method is an effective method for manufacturing holographic optical elements stably and efficiently. During hologram recording, the incident angles of laser beams of a plurality of wavelengths are made different for each wavelength, and diffraction for hologram reproduction is performed. If the wavelength is individually adjusted for each wavelength, the wavelength matching with the light source in the use state can be optimized.

  For example, as shown in FIG. 7A, illumination light C1 having a used wavelength λc (peak) of 520 nm is incident on the holographic optical element HE at an incident angle θi = 45 degrees (inside the medium), and is reproduced by diffraction reflection thereof. Consider a state in which the light C2 is used at an emission angle θc = 135 degrees (within the medium). When the holographic optical element HE is manufactured with a laser beam having an exposure wavelength λr = 532 nm, as shown in FIG. 7B, the incident angle θo of the object light R1 is set to a predetermined angle from the incident angle θi when used. By shifting the holographic optical element HE by a certain amount, it is possible to produce a holographic optical element HE that matches the wavelength λc used. Specifically, correction may be performed under the hologram recording conditions shown in the following Table 1 obtained from the formula (F1).

  Next, an exposure optical apparatus, a manufacturing method, and the like for performing correction that can cope with the above-described deviation between the wavelengths λr and λc will be described. 1 to 4 schematically show schematic sectional structures of exposure optical apparatuses X1 to X4 according to the first to fourth embodiments, respectively. In the production of holographic optical elements having diffraction efficiency peaks at a plurality of wavelengths, the exposure optical devices X1 to X4 irradiate the hologram photosensitive material HK with laser beams KR, KG, KB having a plurality of wavelengths, It performs exposure recording of interference fringes, and includes a light source unit LS, a first optical system L1, a second optical system L2, and the like.

  In the manufacturing method using the exposure optical devices X1 to X4, in the interference fringe exposure recording, one surface S1 of the hologram photosensitive material HK is irradiated with laser beams KR, KG, KB having a plurality of wavelengths, The laser beams KR, KG, KB transmitted through the hologram photosensitive material HK by the irradiation are reflected and re-entered on the hologram photosensitive material HK from the other surface S2, and lasers having a plurality of wavelengths with respect to the one surface S1 of the hologram photosensitive material HK are reflected. By making the incident angles of the light beams KR, KG, and KB different for each wavelength, the diffraction wavelength for hologram reproduction is individually adjusted for each wavelength. In the exposure optical devices X2 to X4, in the exposure recording of interference fringes, laser beams having a plurality of wavelengths that re-enter the hologram photosensitive material HK are irradiated so that their wavefronts are different for each wavelength.

  Here, a sheet-like material is assumed as the form of the hologram photosensitive material HK. However, the hologram photosensitive material HK is not limited to this, and has other forms such as a film formed on a transparent substrate. It may be a thing. In addition, arrows DX, DY, and DZ in the drawings indicate directions orthogonal to each other, and in the rectangular hologram photosensitive material HK, the long side direction is the DX direction and the short side direction is the DY direction. Therefore, the photosensitive material surfaces S1 and S2 are parallel to the DX-DY plane, and the optical axis AX is parallel to the DZ direction in the hologram photosensitive material HK in the exposure optical devices X1 to X4.

  The light source unit LS includes three laser light sources having emission wavelengths corresponding to the three wavelengths of RGB. In the exposure optical devices X1 to X4, three wavelengths of R (red), G (green), and B (blue) are assumed as a plurality of wavelengths. However, the present invention is not limited to this, and other wavelengths are set. May be. Therefore, the oscillation wavelength of the laser light source constituting the light source unit LS is not limited to RGB.

  The first optical system L1 is disposed between the light source unit LS and the hologram photosensitive material HK, and irradiates one of the photosensitive material surfaces S1 of the hologram photosensitive material HK with laser beams KR, KG, and KB having three wavelengths of RGB. To do. The first optical system L1 includes a combiner LC that superimposes RGB three-wavelength laser beams KR, KG, and KB on almost one optical path, and a laser beam KR, KG, that is superimposed on almost one optical path by the combiner LC. And an expander LE that expands the diameter of KB.

  In the exposure optical devices X1 to X4, the three RGB laser beams KR, KG, and KB emitted from the light source unit LS are superimposed on almost one optical path by the combiner LC. They are stacked differently. Examples of the combiner LC include a dichroic mirror, a dichroic prism, and a half mirror.

  The three superimposed laser light beams KR, KG, KB are emitted as substantially parallel light beams having an enlarged diameter by the expander LE, and are irradiated onto the hologram photosensitive material HK. Since the incident angle of the light beam incident on the expander LE is different for each wavelength, the angle of the emitted light from the expander LE is also different for each wavelength. Examples of the expander LE include a Galileo type optical system having a negative and positive power arrangement, a Kepler type optical system having a positive and positive power arrangement, and the use of a Kepler type optical system is assumed here.

  In the exposure optical devices X1 to X4, the laser beam KG is perpendicularly incident on the photosensitive material surface S1 of the hologram photosensitive material HK, and the laser beams KR and KB are obliquely incident on the photosensitive material surface S1 of the hologram photosensitive material HK. To do. That is, the incident angles of the three laser light beams KR, KG, and KB with respect to the photosensitive material surface S1 are different for each wavelength. Then, the laser light beams KR, KG, KB transmitted through the hologram photosensitive material HK by being emitted from the photosensitive material surface S2 are incident on the second optical system L2.

  The second optical system L2 reflects the laser light beams KR, KG, KB emitted from the first optical system L1 and transmitted through the hologram photosensitive material HK, and re-enters the hologram photosensitive material HK, whereby the hologram photosensitive material HK The other photosensitive material surface S2 is irradiated with RGB three-wavelength laser beams KR, KG, KB. In order to reflect the laser beams KR, KG, and KB, the second optical system L2 includes a reflective optical element including a curved reflecting surface that reflects the laser beams KR, KG, and KB. The exposure optical devices X1 to X3 have a concave mirror MC, and the exposure optical device X4 has a dichroic laminated mirror MD. As described above, the second optical system L2 includes the reflecting optical element including the curved reflecting surface as the reflecting surface, so that the holographic optical element HE to be manufactured has not only a deflection function but also an optical for diverging and condensing. Power can be given.

  Laser beams KR, KG, KB emitted from the first optical system L1 and incident on the hologram photosensitive material HK; laser beams KR, KG, KB emitted from the second optical system L2 and re-entered on the hologram photosensitive material HK; Interference fringes FK are formed in the overlapping region (FIGS. 5A and 7B), and the interference state is recorded as hologram interference fringes FE (FIGS. 5B and 7A). ). At this time, as described above, the fringe interval Λ of the recorded interference fringes FK can be set by varying the incident angles of the laser beams KR, KG, KB with respect to the photosensitive material surface S1 of the hologram photosensitive material HK for each wavelength. Control is performed individually (FIGS. 6A and 6B), and the diffraction wavelength (use wavelength) for hologram reproduction is individually adjusted for each wavelength. By the adjustment, it is possible to correct the aberration caused by the difference between the exposure wavelength at the time of hologram recording and the used wavelength at the time of hologram reproduction, and to efficiently use the light source light amount. That is, the color reflection type holographic optical element HE having a diffractive structure in which wavelength matching with the light source in the use state is optimized can be stably and efficiently manufactured by one-beam exposure.

  The exposure optical apparatus X1 (FIG. 1) according to the first embodiment has a basic configuration for performing the above correction. The laser light beams KR, KG, KB transmitted through the hologram photosensitive material HK are reflected by the concave reflecting surface SC of the concave mirror MC constituting the second optical system L2 to be condensed, and enter the hologram photosensitive material HK again. Then, the laser light beams KR, KG, KB incident on the photosensitive material surface S1 from the first optical system L1, and the laser light beams KR, KG, KB folded back by the second optical system L2 and incident on the photosensitive material surface S2. In the overlapped area, exposure recording of the corrected interference fringes is performed. A condensing point of each wavelength is located on the image plane IM0.

  Further, the second optical system L2 in the exposure optical devices X2 to X4 further includes a correction optical element that makes the wavefronts of the RGB three-wavelength laser beams KR, KG, KB re-entering the hologram photosensitive material HK different for each wavelength. Have. As the correction optical element, the exposure optical device X2 (FIG. 2) has a wedge prism PR, and the exposure optical device X3 (FIG. 3) has a diffractive optical element DO. Further, the exposure optical device X4 (FIG. 4) has a dichroic laminated mirror MD, assuming that the reflection optical element and the correction optical element are integrated.

  The correcting optical elements such as the wedge prism PR and the diffractive optical element DO are for giving a chromatic aberration correcting function to the holographic optical element. The relationship between the chromatic aberration and the holographic optical element that corrects it will be described below.

  FIG. 8A shows an optical system that forms an image of a parallel light beam K1 at one point on the image plane IM with a reflective holographic optical element H1. The light beam K1 incident on the optical system is obtained by superimposing, for example, light beams of three wavelengths of RGB respectively emitted from three LEDs into parallel light beams. The holographic optical element H1 is a color holographic optical element in which three holograms (color holograms) having diffraction efficiency peaks at three wavelengths of RGB are recorded.

  Here, as shown in FIG. 8B, when the wedge prism P1 is disposed between the holographic optical element H1 and the image plane IM, the vertical direction (optical axis AX direction, depth direction) DA and the horizontal direction (light A color shift (that is, chromatic aberration) occurs in the direction DB perpendicular to the axis AX and the deflection direction (ie, chromatic aberration), making it impossible to form an image with high resolution. This chromatic aberration can be corrected by the chromatic aberration generated in the opposite directions DA and DB. The holographic optical element HE shown in FIG. 8C has a chromatic aberration correction function, and is configured to correct the chromatic aberration generated by the wedge prism P1 with the chromatic aberration generated by the holographic optical element HE. ing.

  As in the exposure optical devices X2 to X4, the correction optical element of the second optical system L2 is configured to make the wavefronts of the RGB three-wavelength laser beams KR, KG, KB irradiating the hologram photosensitive material HK different for each wavelength. By doing so, it is possible to correct the chromatic aberration by adjusting the reproduction wavefront of the holographic optical element HE for each wavelength. The first optical system L1 irradiates one of the photosensitive material surfaces S1 of the hologram photosensitive material HK with laser beams KR, KG, and KB having three wavelengths of RGB, and the second optical system L2 irradiates the first optical system. The other three photosensitive material surfaces of the hologram photosensitive material HK are reflected from the RGB three-wavelength laser beams KR, KG, and KB that have been emitted from L1 and transmitted through the hologram photosensitive material HK, and are incident again on the hologram photosensitive material HK. If it is configured to irradiate S2, efficient and stable one-beam exposure is possible. Therefore, the holographic optical element HE having a high chromatic aberration correction function can be manufactured stably and efficiently. In order to make it possible to adjust and control the reproduction of the wavefront for each wavelength, it is preferable that the holographic optical element HE to be manufactured is a reflection type having high wavelength selectivity.

  In the exposure optical apparatus X2 (FIG. 2) according to the second embodiment, the laser beams KR, KG, KB transmitted through the hologram photosensitive material HK enter the wedge prism PR in the second optical system L2. The wedge prism PR is a spectroscopic refracting optical element (transmission optical element), and makes the wavefronts of the laser light beams KR, KG, KB different for each wavelength by a refracting action. As a result, the laser beams KR, KG, KB are dispersed with different deflection directions and optical path lengths for each wavelength. The laser beams KR, KG, KB transmitted through the wedge prism PR are reflected by the concave reflecting surface SC of the concave mirror MC to be condensed, and enter the wedge prism PR again. The laser beams KR, KG, and KB are dispersed again by the wedge prism PR with the deflection direction and the optical path length being different for each wavelength, and then emitted from the wedge prism PR.

  The laser beams KR, KG, KB transmitted through the wedge prism PR enter the hologram photosensitive material HK again. Then, the laser light beams KR, KG, KB incident on the photosensitive material surface S1 from the first optical system L1, and the laser light beams KR, KG, KB folded back by the second optical system L2 and incident on the photosensitive material surface S2. Interference fringe exposure recording is performed in the overlapped area. The laser beams KR, KG, and KB that are re-incided at this time have different wavefronts for each wavelength from the first incident (the RGB condensing points are different in both the vertical direction DA and the horizontal direction DB), and are recorded in color. The reproduction wavefront of the hologram is also different for each wavelength. That is, it is possible to manufacture the holographic optical element HE (FIG. 8C) having a high chromatic aberration correction function by providing the hologram photosensitive material HK with a function of correcting the chromatic aberration of the entire optical system to be incorporated.

  The second optical system L2 of the exposure optical apparatus X2 includes a concave mirror MC including a concave reflecting surface SC that reflects the laser beams KR, KG, and KB, and RGB three-wavelength laser beams KR, that irradiate the hologram photosensitive material HK. And a wedge prism PR that makes wavefronts of KG and KB different for each wavelength. The wedge prism PR disposed between the hologram photosensitive material HK and the concave reflecting surface SC has the respective laser beams KR, KG, so that the deflection directions of the RGB three-wavelength laser beams KR, KG, KB are different. By refracting KB, the wavefront is made different for each wavelength (color shift is arranged in order of wavelength), so the difference in deflection direction corresponds to the correction of chromatic aberration in the lateral direction DB, and the dispersion of the wedge prism PR. The optical path length difference for each wavelength due to the above corresponds to correction of chromatic aberration in the longitudinal direction DA. Therefore, the adjustment of the color misregistration amount by the wavelength can be performed by using the wedge inclination (degree of deflection) in the horizontal direction DB and the thickness (optical path length) of the wedge prism PR in the vertical direction DA as parameters. Note that the position of the image plane IM, which is a condensing point of each wavelength, is shifted from the position of the image plane IM0 when there is no wedge prism PR.

  In the exposure optical apparatus X3 (FIG. 3) according to the third embodiment, the laser beams KR, KG, KB transmitted through the hologram photosensitive material HK enter the diffractive optical element DO in the second optical system L2. The diffractive optical element DO is a spectroscopic surface relief type / transmission type diffractive optical element having a one-dimensional blazed diffractive surface SD on the concave mirror MC side (the direction perpendicular to the plane of FIG. 3 is horizontal). This is a one-dimensional direction for obtaining a condensing point difference in the direction DB.) The wave fronts of the laser light beams KR, KG, KB are made different for each wavelength by the diffraction action. As a result, the laser beams KR, KG, and KB that have passed through the diffractive optical element DO are dispersed with different deflection directions and optical path lengths for each wavelength. The laser beams KR, KG, KB transmitted through the diffractive optical element DO are reflected by the concave reflecting surface SC of the concave mirror MC to be condensed, and enter the diffractive optical element DO again. The laser beams KR, KG, and KB are dispersed again by the diffractive optical element DO so that the deflection direction and the optical path length are different for each wavelength, and then exit from the diffractive optical element DO. The diffractive surface SD may be provided on the surface of the diffractive optical element DO on the hologram photosensitive material HK side, and the shape of the diffractive optical element DO is not limited to a parallel plate shape, and may be a wedge prism shape.

  The laser beams KR, KG, KB transmitted through the diffractive optical element DO enter the hologram photosensitive material HK again. Then, the laser light beams KR, KG, KB incident on the photosensitive material surface S1 from the first optical system L1, and the laser light beams KR, KG, KB folded back by the second optical system L2 and incident on the photosensitive material surface S2. Interference fringe exposure recording is performed in the overlapped area. The laser beams KR, KG, and KB that are re-incided at this time have different wavefronts for each wavelength from the first incident (the RGB condensing points are different in both the vertical direction DA and the horizontal direction DB), and are recorded in color. The reproduction wavefront of the hologram is also different for each wavelength. That is, it is possible to manufacture the holographic optical element HE (FIG. 8C) having a high chromatic aberration correction function by providing the hologram photosensitive material HK with a function of correcting the chromatic aberration of the entire optical system to be incorporated.

  The second optical system L2 of the exposure optical device X3 includes a concave mirror MC including a concave reflecting surface SC that reflects the laser light beams KR, KG, and KB, and RGB three-wavelength laser light beams KR and irradiating the hologram photosensitive material HK. And a diffractive optical element DO that makes the wavefronts of KG and KB different for each wavelength. The diffractive optical element DO arranged between the hologram photosensitive material HK and the concave reflecting surface SC has the laser beams KR and KG so that the deflection directions of the RGB three-wavelength laser beams KR, KG and KB are different. , KB are diffracted to make the wavefronts different for each wavelength (the color misalignment is arranged in the order of the wavelength), so that the difference in the deflection direction corresponds to the chromatic aberration correction in the lateral direction DB, and the diffractive optical element DO. The optical path length difference for each wavelength due to the dispersion of the wavelength corresponds to the chromatic aberration correction in the longitudinal direction DA. Therefore, the amount of color misregistration by wavelength can be adjusted using the diffraction power (degree of deflection) in the horizontal direction DB and the thickness (optical path length) of the diffractive optical element DO in the vertical direction DA as parameters. Since the dispersion of the diffractive optical element DO is large, it is possible to give a larger deflection difference. As a result, the degree of freedom of arrangement of the second optical system L2 is improved, and an effective thinning is possible. Note that the position of the image plane IM, which is the condensing point of each wavelength, is shifted from the position of the image plane IM0 when there is no diffractive optical element DO.

  In the exposure optical apparatus X4 (FIG. 4) according to the fourth embodiment, the laser light beams KR, KG, KB transmitted through the hologram photosensitive material HK enter the dichroic laminated mirror MD constituting the second optical system L2. To do. The dichroic laminated mirror MD is a spectroscopic reflective optical element having R reflecting surfaces SR, G reflecting surfaces SG and B reflecting surfaces SB as curved dichroic reflecting surfaces. Laser light beams KR, KG are reflected by wavelength selective reflection. , KB wavefronts are made different for each wavelength. As a result, the laser beams KR, KG, and KB have different focal positions for each wavelength, and are emitted in a condensed state by reflection on the concave reflecting surface SC. At this time, only the R laser beam KR is reflected on the R reflecting surface SR, only the G laser beam KG is reflected on the G reflecting surface SG, and only the B laser beam KB is reflected on the B reflecting surface SB.

  The laser beams KR, KG, KB reflected by the dichroic laminated mirror MD are incident on the hologram photosensitive material HK again. Then, the laser light beams KR, KG, KB incident on the photosensitive material surface S1 from the first optical system L1, and the laser light beams KR, KG, KB folded back by the second optical system L2 and incident on the photosensitive material surface S2. Interference fringe exposure recording is performed in the overlapped area. The laser beams KR, KG, and KB that are re-incided at this time have different wavefronts for each wavelength from the first incident (the RGB condensing points are different in both the vertical direction DA and the horizontal direction DB), and are recorded in color. The reproduction wavefront of the hologram is also different for each wavelength. That is, it is possible to manufacture the holographic optical element HE (FIG. 8C) having a high chromatic aberration correction function by providing the hologram photosensitive material HK with a function of correcting the chromatic aberration of the entire optical system to be incorporated.

  The second optical system L2 of the exposure optical apparatus X4 reflects the laser beams KR, KG, and KB, and the wavefronts of the RGB three-wavelength laser beams KR, KG, and KB that irradiate the hologram photosensitive material HK for each wavelength. It consists of a dichroic laminated mirror MD having different R reflecting surfaces SR, G reflecting surfaces SG and B reflecting surfaces SB as curved dichroic reflecting surfaces. The reflection optical element and the correction optical element are integrated by having the dichroic reflection surfaces SR, SG, and SB that react to specific wavelengths as curved reflection surfaces, respectively, and the RGB three-wavelength laser beams KR, KG, By reflecting each laser beam KR, KG, KB so that the focal position of KB is different, the wavefront is made different for each wavelength, so the difference in focal position corresponds to the correction of chromatic aberration in the horizontal direction DB and the vertical direction DA. . Therefore, the adjustment of the color misregistration amount depending on the wavelength is mainly performed on the reflection surfaces SR, SG, and SB in the horizontal direction DB and the inclination (reflection angle and degree of deflection) of each reflection surface SR, SG, and SB in the vertical direction DA. Curvature and spacing (optical path length) can be used as parameters.

  As in the exposure optical devices X2 and X3, in the correction optical element using the refraction action or the diffraction action, the color shift is arranged in order of wavelength (continuous change), whereas the dichroic of the exposure optical apparatus X4. In the multilayer mirror MD, since the dispersion does not use a refracting action or a diffracting action, individual wavefront adjustment is possible for each wavelength. For example, in the exposure optical apparatuses X2 and X3, the condensing point positions in the vertical and horizontal directions DA and DB are in the order of RGB, whereas in the exposure optical apparatus X4, the condensing point position in the horizontal direction DB is in the order of RBG and vertical. The condensing point positions in the direction DA are in the order of BRG. As described above, the wavelength order restriction on the RGB condensing positions is removed, and the wavefront adjustment control can be performed independently and independently for each wavelength in both the vertical and horizontal directions DA and DB, so that chromatic aberration correction with a high degree of freedom is possible. is there.

  Further, like the exposure optical device X4, it is preferable that the reflection at the RGB three-wavelength dichroic reflection surfaces SR, SG, and SB is back surface reflection. When the back surface reflection is performed, the optical path length difference with respect to the wavelength is generated by the light beam passing through the glass type block. By adjusting this, the chromatic aberration correction in the longitudinal direction DA can be dealt with. That is, when the back surface reflection is used, the same operation as that of the wedge prism PR (FIG. 2) can be achieved by one mirror block (dichroic laminated mirror MD in the exposure optical device X4).

  FIGS. 9A and 9B schematically show schematic sectional structures of the exposure optical apparatuses X5 and X6 according to the fifth and sixth embodiments, respectively. The exposure optical devices X5 and X6 are examples in which the above-described exposure optical devices X1 to X4 are improved for tiling, and a plurality of regions corresponding to a plurality of holographic optical elements HE (the boundaries of the regions are indicated by dotted lines). Interference fringe exposure recording is performed on a single sheet-like hologram photosensitive material HK having the above. A plurality of holographic optical elements HE (FIG. 8, etc.) can be obtained by cutting a sheet-like hologram photosensitive material HK subjected to exposure recording or the like at the boundary of the region (dotted line in FIG. 9). . 9 (A) and 9 (B) both show the state viewed from the DX direction except for the hologram photosensitive material HK, and it is understood that the shape of each region is rectangular with respect to the hologram photosensitive material HK. In order to facilitate, the state seen from the DZ direction is shown.

  In the exposure optical apparatus X5 shown in FIG. 9A, laser light beams KR, KG, KB emitted from one light source unit LS enter the hologram photosensitive material HK through one first optical system L1. At this time, the laser beams KR, KG, and KB that enter the hologram photosensitive material HK from the first optical system L1 are substantially parallel beams consisting of one set of each of the RGB wavelengths (that is, the plurality of regions for each wavelength). Is a substantially parallel light beam covering A plurality of second optical systems L2 are arranged in the DY direction along the surfaces S1, S2 of the hologram photosensitive material HK, and laser beams KR, KG, KB emitted from the first optical system L1 and a plurality of second optical systems L2. The laser beams KR, KG, KB emitted from the laser beam are simultaneously incident on the hologram photosensitive material HK, so that exposure recording corresponding to a plurality of holographic optical elements HE is simultaneously performed. By using the exposure optical device X5 thus tiled, a large number of holographic optical elements HE can be manufactured simultaneously.

  In the exposure optical apparatus X6 shown in FIG. 9B, a plurality of first and second optical systems L1, L2 are arranged in the DY direction along the surfaces S1, S2 of the hologram photosensitive material HK. Laser beams KR, KG, KB emitted from the plurality of light source units LS enter the hologram photosensitive material HK through the plurality of first optical systems L1. At this time, the laser light beams KR, KG, KB incident on the hologram photosensitive material HK from the plurality of first optical systems L1 are substantially parallel light beams composed of a plurality of sets each having one wavelength of RGB (that is, the plurality of light beams for each wavelength). A plurality of substantially parallel light fluxes corresponding to the region (1). By causing the laser beams KR, KG, KB emitted from the plurality of first optical systems L1 and the laser beams KR, KG, KB emitted from the plurality of second optical systems L2 to simultaneously enter the hologram photosensitive material HK, a plurality of Exposure recording corresponding to the holographic optical element HE is simultaneously performed. By using the exposure optical device X6 thus tiled, a large number of holographic optical elements HE can be manufactured simultaneously. In addition, since a degree of freedom can be given to the light emitted from the first optical system L1, a large number of various holographic optical elements HE can be simultaneously produced.

  In the exposure optical devices X5 and X6, the plurality of regions of the hologram photosensitive material HK are all rectangular, and a plurality of second optical systems L2 are arranged along the DY direction which is the short side direction. When a plurality of the second optical systems L2 are arranged side by side in the short side direction (DY direction) in this way, the area of the hologram photosensitive material HK can be used effectively, so that effective tiling is possible. In particular, as in the case of the exposure optical devices X1 to X4, more effective tiling is possible when the laser beams KR, KG, KB are incident on the hologram photosensitive material HK from the first optical system L1 vertically or substantially perpendicularly. It becomes. In the case of two-dimensional tiling, it is preferable to increase the number of tilings in the short side direction (DY direction) rather than the long side direction (DX direction).

  When the exposure optical devices X5 and X6 are improved for tiling like the exposure optical devices X5 and X6, the laser beams KR, KG, and KB are obliquely incident on the hologram photosensitive material HK from the first optical system L1, and the tilt directions thereof. A plurality of second optical systems L2 are arranged side by side in the direction perpendicular to the (eccentric direction) (DY direction). As described above, when a plurality of the second optical systems L2 are arranged side by side in the vertical direction (DY direction) with respect to the tilt directions (eccentric directions) of the laser beams KR, KG, KB with respect to the hologram photosensitive material HK, the area of the hologram photosensitive material HK is reduced. It can be used effectively, and the tilting direction of the obliquely incident laser beams KR, KG, KB is easily located in the longitudinal direction of the optical set, so that effective tiling is possible. In the case of two-dimensional tiling, it is preferable to increase the number of tilings in the direction perpendicular to the tilt direction (eccentric direction) of the laser beams KR, KG, KB (DY direction).

X1 to X6 Exposure optical device LS Light source (laser light source)
L1 first optical system LC combiner LE expander HK hologram photosensitive material FK interference fringe L2 second optical system PR wedge prism (correction optical element)
MC concave mirror (reflection optical element)
SC Concave reflective surface (curved reflective surface)
DO diffractive optical element (correction optical element)
SD Diffraction surface MD Dichroic laminated mirror (reflection optical element, correction optical element)
SRR reflective surface (curved reflective surface, dichroic reflective surface)
SGG reflective surface (curved reflective surface, dichroic reflective surface)
SB B reflective surface (curved reflective surface, dichroic reflective surface)
MR plane mirror KR, KG, KB Laser beam HE holographic optical element FE Hologram interference fringe S1, S2 Photosensitive material surface R1 Object beam R2 Reference beam C1 Illumination beam C2 Reproduction beam K1 Beam P1 Wedge prism IM0, IM Image plane

Claims (9)

In the manufacture of a holographic optical element having diffraction efficiency peaks at a plurality of wavelengths, a manufacturing method for performing exposure recording of interference fringes by irradiating a hologram light-sensitive material with laser beams having a plurality of wavelengths,
Irradiating one surface of the hologram photosensitive material with a laser beam of the plurality of wavelengths, reflecting the laser beam transmitted through the hologram photosensitive material by the irradiation and re-entering the hologram photosensitive material;
A manufacturing method characterized in that the diffraction wavelength of hologram reproduction is individually adjusted for each wavelength by making the incident angles of the laser beams of the plurality of wavelengths with respect to one surface of the hologram photosensitive material different for each wavelength. Performing exposure recording of the interference fringes using an exposure optical device, the exposure optical device,
A light source unit having a plurality of laser light sources with emission wavelengths corresponding to the plurality of wavelengths;
A first optical system for irradiating one surface of the hologram photosensitive material with the laser beams having the plurality of wavelengths emitted from the light source unit;
Irradiation to the other surface of the hologram photosensitive material by reflecting the laser light beams having the plurality of wavelengths that have been emitted from the first optical system and transmitted through the hologram photosensitive material and reflected again on the hologram photosensitive material. A second optical system,
The first optical system includes a combiner that superimposes the laser beams of the plurality of wavelengths, and an expander that expands the diameter of the laser beam superimposed by the combiner,
The second optical system has a reflecting surface for reflecting the laser beam;
The first optical system individually adjusts the diffraction wavelength of hologram reproduction for each wavelength by differentiating the incident angles of the laser beams of the plurality of wavelengths with respect to one surface of the hologram photosensitive material for each wavelength. The manufacturing method according to claim 1.   The manufacturing method according to claim 2, wherein the second optical system includes a reflective optical element including a curved reflective surface as the reflective surface.   4. The manufacturing method according to claim 2, wherein the second optical system includes a correction optical element that makes the wavefronts of the laser beams having the plurality of wavelengths re-enter the hologram photosensitive material different for each wavelength. .   The correction optical element is disposed between the hologram photosensitive material and the curved reflecting surface, and transmits the laser beams so that the deflection directions of the laser beams of the plurality of wavelengths are different from each other. The manufacturing method according to claim 4, wherein the transmission optical element is made different for each wavelength.   The correction optical element is a diffractive optical element that diffracts each laser beam so that deflection directions of the laser beams of the plurality of wavelengths are different, thereby making the wavefront different for each wavelength. Item 5. The production method according to Item 4.   The correction optical element has a plurality of dichroic reflection surfaces that react to a specific wavelength as the curved reflection surface, thereby being integrated with the reflection optical element, and the reflected wavefronts of the laser beams of the plurality of wavelengths are respectively 5. The manufacturing method according to claim 4, wherein the laser beam is reflected so as to be different so that the wavefront is different for each wavelength.   The manufacturing method according to claim 7, wherein the reflection at the plurality of dichroic reflection surfaces is back surface reflection. In the production of a holographic optical element having diffraction efficiency peaks at a plurality of wavelengths, an exposure optical apparatus that performs exposure recording of interference fringes by irradiating a hologram light-sensitive material with laser beams having a plurality of wavelengths,
A light source unit having a plurality of laser light sources with emission wavelengths corresponding to the plurality of wavelengths;
A first optical system for irradiating one surface of the hologram photosensitive material with the laser beams having the plurality of wavelengths emitted from the light source unit;
Irradiation to the other surface of the hologram photosensitive material by reflecting the laser light beams having the plurality of wavelengths that have been emitted from the first optical system and transmitted through the hologram photosensitive material and reflected again on the hologram photosensitive material. A second optical system,
The first optical system includes a combiner that superimposes the laser beams of the plurality of wavelengths, and an expander that expands the diameter of the laser beam superimposed by the combiner,
The second optical system has a reflecting surface for reflecting the laser beam;
In order that the first optical system individually adjusts the diffraction wavelength of hologram reproduction for each wavelength, the incident angles of the laser light beams of the plurality of wavelengths with respect to one surface of the hologram photosensitive material are made different for each wavelength. An exposure optical apparatus.

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